The main interest in matter wave interferometers is based on the very high sensitivity of these interferometers to accelerations (including gravitation and rotations) and electromagnetic fields, as described, for example, in A. D. Cronin, J. Schmiedmayer, D. E. Pritchard, “Optics and interferometry with atoms and molecules”, Rev. of Mod. Phys. 81, 1051 (2009) (hereinafter called [Ref 1]). Most existing atom interferometers are based on free propagating atoms, which are coherently split by mechanical gratings or non-resonant standing light waves [Ref 1]. On the other hand, there is a great commercial interest in waveguide-type atom interferometers, in which atoms are partially or fully prevented from free falling in a gravitational field and can be integrated into portable atom chips.
Most current waveguide matter-wave interferometers are based on magnetic waveguides. One recent example of such an interferometer based on a double-well beam splitter is described in T. Schumm et al, “Matter-wave interferometry in a double well on an atom chip”, Nature 1, 57 (2005) [Ref 2]. The main problem of these beam splitters is that they work only for magnetically trappable atoms. This means that any environmental magnetic fields will essentially perturb such an interferometer. In addition, the local fluctuations of the surface electric currents, which are used to form the trapping magnetic field, limit the coherence time of the atoms in such types of magnetic traps, unless the current-carrying substrate is cooled down to cryogenic temperatures.
Recently, G. L. Gattobigio et al, “Optically guided beam splitter for propagating matter waves”, Phys. Rev. Lett. 109, 030403 (2012) [Ref 3] has demonstrated a beam splitter based on two crossed laser beams, which relies on chaotic trajectories of atoms and therefore can't be used for atomic interferometry.
G. D. McDonald et al, “Optically guided linear Mach-Zehnder atom interferometer”, Phys. Rev. A, 87, 013632 (2013) [Ref 4] describes ultracold atoms trapped in a single laser beam waveguide. In [Ref 4], splitting of the atoms was performed in a pulsed way, by application to them of an additional optical standing wave. Therefore, this is a temporal (or pulsed) interferometer.
Other background art may be found in the following two documents: Yu. B. Ovchinnikov et al, “An atomic trap based on evanescent light waves”, J. Phys. B: At. Mol. Opt. Phys. 24, 3173 (1991) [Ref 5], and A. H. Barnett et al, “Substrate-based atom waveguide using guided two-colour evanescent light fields”, Phys. Rev. A 61, 1371 (2000) [Ref 6].
A technical challenge, therefore, is to design and build atom interferometer based devices with unprecedented small size, light weight, low power, high performance and low cost characteristics. Compact cold atom sensors (gravimeters, gradiometers) for ultraprecise measurements of inertial and electromagnetic forces, which are based on all-light waveguide atom interferometers of a new type, offer exciting prospects for a wide range of applications.